1. Field of the Invention
The present invention concerns a catheter of the kind used in magnetic-resonant-supported interventional procedures.
2. Description of the Prior Art
In medicine, catheter-supported examination and treatment procedures are established procedures in which usually a long, thin catheter is inserted into a hollow organ of the body.
Catheter-supported procedures are frequently used, for instance, in the vascular system and the heart. For this purpose, a catheter is inserted into well-accessible arm and leg veins or arteries and fed forward to the place to be examined and/or treated. Known examinations performed in the context of intracardiac catheter examinations are, for instance, a representation of hemodynamics by means of injected contrast agents, measurements of the electric activity of the heart in the context of an electrophysiological examination, performance of pressure and/or oxygen measurements in various parts of the circulatory system, a representation of the heart ventricles and coronary vessels balloon dilatation or stenting of constricted vessels, treatment of cardiac defects and ablation of additional stimulation paths or of myocardial tissue.
Depending on the intended use, of the inserted catheter, the catheter tip can have different designs. For ablation of tissue, catheters are known that carry at their tip a probe designed as a high frequency antenna (subsequently also referred to as RF antennas; RF standing for high frequency) by means of which RF energy is discharged into the surrounding tissue in order to coagulate the tissue. Alternatively, probes in the form of ultrasound transducers or laser sources are known by means of which tissue can also be destroyed by means of ultrasound or laser beams. Furthermore, catheters are known that are used for cryoablation (destruction of tissue by means of freezing) or for alcoholic ablation (destruction of tissue by means of injections of alcohol).
Usually, in the process, the catheter is fed forward in the tissue under visual control, which previously has been facilitated by means of X-ray examination. However, in several ways, the use of X-rays is problematic, especially since both the attending physician and the patient are partially exposed to serious radiation levels. In fact, it has been proposed to perform such interventions by remote-control so that at least the attending physician is protected against the X-rays. In this case, a magnetic catheter tip can be navigated by means of an external magnetic field. Even these procedures involve disadvantages. The construction of such a system is comparatively expensive, quick intervention in the event of complications is hindered and possibly a patient might not tolerate the absence of an immediately attending physician.
One possibility of solving this problem at least partially is to use magnetic resonance technology in the form of imaging in interventional procedures instead of X-ray procedures so that radiation exposure during an examination is eliminated.
Magnetic resonance imaging (subsequently referred to as MR imaging, MR standing for magnetic-resonance) is a field in medical imaging that has been successfully established since many years. Very simply stated, by using different magnetic fields of various strengths and spatial and timed characteristics, magnetic resonances are caused in an object to be examined. For this purpose, RF pulses with precisely defined frequencies are radiated by means of RF antennas. The magnetic resonances, on their part, are also being measured with RF antennas. More recently, MR imaging has been used also in the form of imaging during interventional procedures.
The interventional instruments used for such purposes have to be designed so as to be compatible with MR technology. This means that the use of instruments in the environment of MR equipment should not result in significant interferences with MR equipment (for instance, by disturbing sensitively adjusted magnetic fields) or endanger the patient.
For instance, from U.S. Pat. No. 6,701,176, a catheter is known which has at its head an RF antenna for MR imaging and also diagnostic electrodes to receive electric potentials. In addition, the head can have a tip for ablation of tissue. The head of the catheter is flexible and can be bent over control wires. Since the wires leading to the head of such a catheter are designed as electric conductors, there is the danger that the electric conductors are interacting with the RF energy of the MR equipment, which can result in problems. In order for the MR equipment not to be influenced by the HF energy of the ablation system and in order for the ablation system not to be influenced by the RF pulses of the MR equipment, filtering systems are disclosed in order to reduce undesirable HF or RF energy that might have been received.
It is also intended to design catheters in a simple and space-saving manner in order to use them in magnetic-resonant-supported interventional procedures.